Why are you putting these shrimps in with a betta??? I have about 50 RCS shrimps of my own and they always lived in a separate tank. I would never think about putting in a shrimp with my betta tank....unless I wanted the shrimp to be food for the fish.

You didn't mention how much cover they have, but judging from your photos, they don't seem to have much moss or other cover like that. You should get some riccia, some moss, or even some subwassertang and just let it float around in the tank. The betta will enjoy it, too, but it will help to de-stress your shrimp because they like to hide in it - especially when there is a big fish around. They don't care that he's not chasing them - he's there, and they were just chased before! After a while, they'll realize he's not after them and they'll be more comfortable.

For the future, shrimp should always be acclimated with the drip method. They shouldn't be acclimated like fish. The shock of the water is probably part of it.

In the end, keep an eye on them and provide them some cover, and they'll probably bounce back!

What is the drip method?

and they only have 2 plants and a cave to hide in this tank. I could put them in a 21 gallon with a lot of plants but they would probably end up as snack with 3 female bettas, 2 plattys and 3 mollies?

You can expect to lose some shrimp to any fish large enough to eat them if you house them together, but I have kept betta and shrimp together with no problems! It's all about cover!!

True, but you'd have to have the tank so densely planted that you might never even see your shrimps to enjoy them. And the shrimps will forever be stressed trying to hide. Overall, it seems like a waste of money to keep shrimps with bettas....it's like buying feeder shrimp for a tank.

and they only have 2 plants and a cave to hide in this tank. I could put them in a 21 gallon with a lot of plants but they would probably end up as snack with 3 female bettas, 2 plattys and 3 mollies?

As far as the plants go, see if you can just get some moss or something similar for the tank they're in now. That will help them tremendously.

For drip acclimation, you need a large bucket (or bowl), and an air hose. Put the shrimp and the water they came in into the bucket, and use the air hose to siphon water from the tank they are going in. You'll need to clamp the end of the hose that goes into the bowl so that it's just dripping instead of running free. Binder clips work great for this. Let the water drip from the tank into the bucket. After an hour or so, empty some of the water from the bucket and let it continue to drip. You can do this for as long as you want, but a couple of hours is probably sufficient. Once it's done, the shrimp (or fish!) can be safely added to your main tank. This really should be done after a quarantine period in a completely separate tank/bowl.

As far as the plants go, see if you can just get some moss or something similar for the tank they're in now. That will help them tremendously.

For drip acclimation, you need a large bucket (or bowl), and an air hose. Put the shrimp and the water they came in into the bucket, and use the air hose to siphon water from the tank they are going in. You'll need to clamp the end of the hose that goes into the bowl so that it's just dripping instead of running free. Binder clips work great for this. Let the water drip from the tank into the bucket. After an hour or so, empty some of the water from the bucket and let it continue to drip. You can do this for as long as you want, but a couple of hours is probably sufficient. Once it's done, the shrimp (or fish!) can be safely added to your main tank. This really should be done after a quarantine period in a completely separate tank/bowl.

Hmmm okayy thank you, i have fish bowls i dont use so im ready for the next time :)

waiit what black spot? I only see the shrimps organs which seems to make a dark patch on the shrimp....

If your shrimps survive, you'd be surprise at good they are at hiding...
O thought for the longest time I had 4 rcs in my 2.5 gallom betta tank.
after rehomeing all 4... I found 4 more...the last one when I was just about to pour my tank out for a rescape, and what I see? A little red thing swimming around in the muddy water o_O

waiit what black spot? I only see the shrimps organs which seems to make a dark patch on the shrimp....

If your shrimps survive, you'd be surprise at good they are at hiding...
O thought for the longest time I had 4 rcs in my 2.5 gallom betta tank.
after rehomeing all 4... I found 4 more...the last one when I was just about to pour my tank out for a rescape, and what I see? A little red thing swimming around in the muddy water o_O

I have large colonies of RCS in both of my tanks, one with a male betta, one with a sorority. I have only occasionally lost a shrimp. Just have plenty of cover (particularly java moss, or other plants that grow densely like lacefern and elodea). In a sparsely planted tank, sure, shrimp aren't a great idea with a betta, but it is perfectly doable. Don't be put off by it. :)

I have large colonies of RCS in both of my tanks, one with a male betta, one with a sorority. I have only occasionally lost a shrimp. Just have plenty of cover (particularly java moss, or other plants that grow densely like lacefern and elodea). In a sparsely planted tank, sure, shrimp aren't a great idea with a betta, but it is perfectly doable. Don't be put off by it. :)

And I agree, those black spot aren't something to worry about.

Thanks man, I noticed they are more active when the lights are off while during the day the 3 of them hide under one fake plant that is filled with algae. They never eat. Is the algae enough for them?

I can't help with the black spots having never seen anything like that on my shrimp but I thought I'd let you know that when they are kept on white gravel, they will often loose their color so they blend in more.
My mom always liked my shrimp so she got some for a 5 gallon and within a couple weeks, they all turn pale like ghost shrimp.
I also have kept mine in all my tanks, whether a community or a betta set up. I suppose some do get eaten but not enough to notice. I have two in a 10 gallon with my new male, he follows them around but never gets too close or tries to eat them. They give him something to interact with.